1. Field of the Invention
The present invention relates to multipoint videoconference systems, and more particularly, to a videoconference system, as well as to its constituent devices, in which a plurality of videoconference terminals, a videoconference server, and a videoconference administration server are interconnected via an ATM network.
2. Description of Related Art
Videoconference systems provide both voice and video communications between remotely located multiple parties. One of the key aspects of today's increasing market demands for videoconference systems is the provision of more realistic conference environments with a greater channel bandwidth.
Conventional videoconference systems realize multipoint teleconferencing by using the ITU-T H.261 videoconferencing coding standards and the narrow band ISDN (N-ISDN) communication channels for signal transmission. In such systems, audio and video information is transferred between a plurality of conference rooms over a single or multiple 64 kbps ISDN transmission channels.
However, the quality of video information reproduced at the receiving ends is not satisfactory at all because of its slow frame rate. The conventional systems are unable to represent detailed expression and smooth motion of participants of a conference.
Furthermore, the conventional videoconference can only send voice and video information, but during the session of a videoconference, it cannot transfer materials such as text, photos, illustrations, and graphs that the participants prepared for the conference. Although it is possible to transmit visual images of such documents via the video camera, instead of sending pictures of the participants, the system does not support realtime distribution of material data in the middle of a conference concurrently with the audio and video information.
The above-described problems may be solved by adding more capacity, or bandwidth, to the communications channels allocated. However, this cannot be a practical solution because it will cause an unacceptably high communication cost.
Delivery of a variety of reference materials, particularly when it occurs concurrently with the voice and video information, will require separate channels having different bandwidths each suitable for their properties. However, such a system is not feasible because it leads to inefficient usage of communication channels in the existing network technologies. Therefore, new videoconference systems that meet the above-described requirements have been demanded.